


Spider-Man's Very Mundane Kryptonite

by whumphoarder



Series: Lactose Intolerant Peter [1]
Category: Marvel Cinematic Universe, Spider-Man - All Media Types, Spider-Man: Homecoming (2017), The Avengers (Marvel Movies)
Genre: Gen, Iron Dad, Irondad, Lactose Intolerance, Mentor/Protégé, Mild Hurt/Comfort, Platonic Relationships, Sick Peter Parker, Sickfic, Stomach Ache
Language: English
Status: Completed
Published: 2018-09-09
Updated: 2018-09-09
Packaged: 2019-07-08 19:38:04
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,533
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/15936917
Author URL: https://archiveofourown.org/users/whumphoarder/pseuds/whumphoarder
Summary: Spider-Man does whatever a Spider can. If only digesting lactose were one of those things.Or, where Peter is unfortunately lactose intolerant and Tony finds out.





	Spider-Man's Very Mundane Kryptonite

The spider bite had cleared up a number of Peter Parker’s physical issues overnight—his eyesight had improved, his immune system skyrocketed, his muscles strengthened—and that’s not even to mention the super healing and the whole ‘sticking to walls’ thing. But one thing the mutated DNA had _not_ addressed, was his body’s inability to digest dairy products.  
  
His aunt and uncle had put two and two together and figured out he was lactose intolerant at the age of nine. That particular night, he’d been curled up on the sofa with the worst stomach ache of his life following a classmate’s birthday party. The giveaway had been when Peter recalled the party’s menu: homemade mozzarella sticks, four-cheese lasagna, and an ice cream cake. He’d thrown up twice before the night was out, once all over Uncle Ben’s new shoes.  
  
Thankfully, his condition was relatively mild these days. Trial and error had taught Peter that he could still handle some dairy without consequence. A piece of pizza here and there, or the occasional celebratory trip to the frozen yogurt bar with the decathlon team, he could manage with no problem. The difficult part was always having to limit himself, something that had only gotten harder as his appetite increased with the mutation.  
  
But today, Peter would argue, it really wasn’t his fault.  
  
“Hey, do we have any more almond milk?” Peter asked that morning, pouring the last drops of the nearly empty carton on his dry Cheerios.  
  
“Oh shoot, I forgot to buy it yesterday,” Aunt May replied. “I’m sorry, bud. Want some eggs?”  
  
“Nah it’s fine, I don’t wanna be late,” Peter said, pulling out the regular milk from the fridge instead. That amount of dairy wouldn’t hurt him, so long as he was careful the rest of the day. He downed his cereal quickly, gave May a quick kiss on the forehead, and hurried off to school.

 **X**  
  
Third period was Spanish. As Peter stepped into the classroom, his senses were instantly overwhelmed by the abundance of colorful crepe paper decorations hanging on the walls and the upbeat Latin music video playing on the SMART Board.  
  
“Bueños Dias, Señor Parker!” his teacher greeted. “Ready for today’s fiesta?”  
  
“Oh yeah! That was today...” Peter recalled.  
  
“You can put your potluck dish over there,” his teacher continued, pointing to the corner of the classroom where a handful of students were already congregating around a table full of various dishes. Peter nodded and moved over to join the crowd. Digging through his bag, he found a couple of partly smushed granola bars he had brought for later and tossed them onto the overflowing table.  
  
A girl snorted at him. “That’s pathetic, Parker. A new low for white boys everywhere.”  
  
“Shut up, MJ,” he giggled back.  
  
**X**  
  
By lunch, Peter’s stomach wasn’t too happy about his earlier choices. It growled mutinously at him as he picked at his sandwich and carrot sticks.  
  
“Dude,” Ned commented, amused. “Was that a velociraptor?”  
  
Peter grinned sheepishly and rubbed at his noisy gut. “My stomach’s kinda upset...” It let out another groan.  
  
“No kidding,” Ned snorted. “You had dairy again, didn’t you?”  
  
“Not a lot!” Peter defended, but his stomach betrayed him with yet another growl. “Alright, maybe it was a lot. We had the end of finals party in Spanish class and Gabriella’s grandmother sent her in with like, three whole pans of enchiladas. And Chelsea brought nachos.” He rubbed his stomach with a wince. “Oh yeah and Cesar’s mom made this awesome flan too...”  
  
Ned rolled his eyes good-naturedly. “As your Official Guy In The Chair, I feel like it’s my duty to remind you that despite your freakishly awesome powers, you are still a mostly-human being with a digestive system that sometimes sucks at being a digestive system and so you’ve really gotta stop doing this to yourself, man."

"I know," Peter groaned.

"...However, given that this particular instance includes free enchiladas made by an authentic Mexican abuela...” Ned shrugged and concluded solemnly, “Some causes are worth dying for."

Peter huffed out a laugh. “Yeah.” He sighed, letting his gaze fall defeatedly to his lunch. “Want the rest of my PB&J?”  
  
Ned perked up. “Strawberry jelly?”  
  
“Nah, grape.”  
  
Ned looked horrified. “What are you, a barbarian?!”

(He took the sandwich anyway.)  
  
**X**  
  
By the time Happy arrived to pick him up later that afternoon, Peter was feeling mostly better. He had been looking forward to this day for weeks now — the kickoff to a whole weekend of training at the compound with the Avengers — and the excitement was enough to take his mind off the lingering discomfort as his body worked to finish digesting that morning’s misfortune.  
  
“Hey kiddo,” Mr. Stark said the moment he stepped inside, clapping Peter on the back amiably. “Go drop your stuff off and get changed. We’re meeting in the gym for a training session. Then dinner, and then I’ve got a surprise I think you’re gonna love.”  
  
Peter grinned and hurried off to suit up.  
  
Twenty minutes later, the team had assembled in the gym for an alien attack simulation exercise. Peter was teamed up with the Scarlet Witch, Hawkeye, and Falcon, working on the outskirts of the massive training facility to create a perimeter while the Avengers who were more adept at combat battled in the center. Peter had never been more grateful for his full-face mask since he was grinning beneath it stupidly the whole time. Fighting alongside actual superheroes and earning the occasional “Nice one, kid!” or “Good work!” comments as he fired webs and delivered kicks was fulfilling about six of his childhood dreams at once.  
  
After the simulation was complete, they all changed out of their suits and into civilian clothes and Tony announced that dinner had arrived, so all those ungrateful freeloaders had better get it while it was hot. Peter was famished by this point (especially since he’d barely ate lunch and had donated his usual after-school snacks to the Spanish cause). He moved eagerly to join the queue of heroes heading toward the kitchens.  
  
It just had to be pizza, didn’t it?  
  
Peter’s heart sank as he gazed at the stacks of steaming cardboard boxes in longing. The aroma was heavenly. It was clear that Mr. Stark had ordered them from an authentic, likely very expensive restaurant. He figured he could get away with a slice or two - maybe more if he scraped the cheese off.  
  
His stomach growled, but in anticipation this time, and it earned him a chuckle from Captain America himself.  
  
“You can go ahead and cut in, kid,” Steve offered. “It’s not every day I meet someone with a metabolism to match mine.”  
  
“Oh no that’s alri-“ Peter began to say back. But he was cut off by a familiar scientist’s voice.  
  
“I think it’s faster, actually,” Bruce Banner noted as he picked a couple of pieces of supreme pizza from a box. “He’s still an adolescent so if it happens to be during a growth spurt, his metabolic rate could be five to six times that of a non-enhanced person.”  
  
“Jeez, kid,” Sam commented.  
  
“All the more reason to get some food in him ASAP!” Steve gave Peter a pat on the shoulder and nudged him forward.  
  
His cheeks flushing in embarrassment, Peter grabbed two pieces of pepperoni from the box closest to him and tried to duck out of the line. But Hawkeye only balked at him in response.  
  
“You don’t have to be shy,” Clint said with a laugh. “Big appetites come with the territory, which is probably why Stark bought half of Italy here.” He gestured broadly, encompassing the mountain of pizza boxes.  
  
“You laugh now, Legolas, but it would be even worse if Thor was in town,” Tony argued. “Or in the realm, I should say,” he amended. “His record is seven pies in one night, and that was _deep dish_.”  
  
Reluctantly, Peter grabbed a piece of Hawaiian and something with green peppers on it to add to his pile. This then prompted the Avengers to deteriorate into the classic argument of whether or not pineapple belongs on pizza, but Peter was grateful because at least it got the focus off of how much he was consuming.  
  
To the poor kid’s simultaneous delight and dismay, the food tasted every bit as glorious as it smelled. He found himself devouring all four slices, as well another two before he could stop himself. Though he did manage to inconspicuously pick off and dispose of about a slice-and-a-half’s worth of cheese, so he counted that as a win.  
  
“Alright everyone,” Tony announced as dinner was winding down. “I told you I had some news. You all know how Ben  & Jerry’s came out with a new ice cream flavor a few weeks ago, inspired by yours truly?”  
  
“Yeah, Stark Raving Hazelnut,” Clint supplied. “Bit chalky, wasn’t it?”  
  
“Could have used more chocolate,” Natasha remarked.  
  
“And fewer hazelnuts,” Sam added, making a face.  
  
“No, I thought the hazelnuts were good,” Bruce argued, “but it needed another texture component. It was pretty one-dimensional.”  
  
“Yeah, I can see that,” Steve allowed. “Maybe caramel?”  
  
Clint nodded thoughtfully, “That might have helped with the chalkiness...”  
  
“ _Anyway,_ ” Tony said loudly over the chatter. “The point is that was only the beginning. Ben & Jerry’s informed our PR team that they have been working on a new line of flavors to commemorate ‘Earth’s Mightiest Defenders’"—he put air quotes around the term— “and they’ll be releasing a new flavor every week this summer.”  
  
Interested murmurs filled the room as Tony moved over to what appeared to be a sheet-covered box on his left. With a flourish, Tony whipped the cloth off, revealing a glass-topped chest freezer stuffed to the brim with ice cream pints. “Would anyone like to do some product testing?”  
  
**X**  
  
Given that his stomach was already not too happy about dinner, Peter had tried his best to avoid the ice cream buffet altogether. But this turned out to be nearly impossible when he was repeatedly requested to settle disputes by bickering teammates over which flavors were better by sampling one pint or another (which Mr. Stark was almost always involved in). And it didn’t help that they were all delicious either—Black Widow Cherry Forest was a top contender, along with Strawberry Slinging Spider-Man, of course. The only one that was a resounding flop was Bruce’s flavor—Hulkin’ Hunks of Sweet Jalapeño.  
  
To make matters worse, training started up again just as soon as the ice cream was gone, this time with the team splitting into small groups to work on hand-to-hand combat. Peter went a few rounds with Wanda, but he was struggling. Despite his efforts to conceal his distress, his stomach groaned and cramped with every movement and he wanted nothing more than to curl up on the couch and wait for this to pass.  
  
Peter carefully picked himself off the mat after Wanda’s third time laying him out.  
  
“I had expected more of a fight from you, Spider-Man,” she said with a smirk. “I sincerely hope you’re not going easy on me because I’m a girl, because I’ll have you know I could drop you in a heartbeat.”  
  
Peter tried to return the smirk, but it was forced. “Just getting warmed up.” But then, his insides cramped in a different way and Peter panicked.  
  
“Sorry, I... I’ll be right back,” he choked out. “Maybe you and Mr. Falcon can practice...?” He didn’t wait for an answer before hurrying out of the gym and into the main compound towards the nearest bathroom.  
  
Twenty minutes later, Peter emerged from the restroom significantly paler and sweatier than before. His stomach was still cramping fiercely and he felt terrible. The last thing in the world he wanted to do was more sparring, but at the same time, he knew he would have to get back out there before anyone came looking for him.  
  
Too late. “Hey kid, Wanda said you disappeared.”  
  
Peter startled at the unexpected voice as he stepped out into a hallway. “Oh! Mr. Stark!” he exclaimed. “I was just coming back out, sorry!”  
  
Tony’s expression changed to one of mild concern as he took in Peter’s pale appearance. “You feeling okay, kiddo?”  
  
“Yeah, totally,” Peter said quickly. Just then his stomach cramped again and he couldn’t hold back the grimace this time. “Actually... um, I’ll be right back.” He turned on his heel and headed back to the bathroom.  
  
This time when Peter returned, Tony was sitting casually on the sofa and scrolling through his phone. He glanced up when Peter entered and wordlessly handed him a glass of water from the table next to him. Peter took it with a mumbled thanks.  
  
“Hey. Talk to me kid.” Tony slipped his phone back into his pocket. “What’s going on?” he asked.  
  
Peter was about to insist he was fine again when his stomach gave a loud, angry growl, causing Tony to raise his eyebrows. Peter decided there was no use pretending anymore. “I’m sorry, Mr. Stark. I’m just... I’m not feeling so great.” He sunk down on the couch next to his mentor and groaned softly. “My stomach really hurts.”  
  
Tony gave an understanding nod. “I figured. Did you get sick, or what?”  
  
“I think I just ate too much,” Peter mumbled back. He let his arms wrap around his churning gut. “I’d already had some milk and cheese earlier and then there was the cheese on the pizza, and then the ice cream...”  
  
Tony frowned and held up a hand. “Hang on, I’m gonna stop you right there. Are you telling me you’re _lactose intolerant_?”  
  
Peter’s gaze shifted to his feet. “Um... Kind of.”  
  
Tony blinked. “Peter. We’ve had this little mentorship thing going for, what? Eight months? And you’re just mentioning this _now_?”  
  
“Well it’s never really come up before...”  
  
Tony scowled. “Never come up? I order us pizza like every other time you visit! And in all this time you never thought to mention I was effectively _poisoning_ you a couple times a month?”  
  
“No, no Mr. Stark, it’s really not that bad! And the pizza is always great!” Peter insisted. “I just... get stomach aches sometimes.”  
  
“But why wouldn’t you say anything before?”  
  
“I didn’t want to cause any trouble,” he said earnestly. “And it’s not like I’ll _die_...”  
  
Tony shook his head slowly in disbelief. “You’re allowed to have food allergies, kid. I mean, I already get Nat special orders because she doesn’t eat gluten.”  
  
Peter was surprised. “You do?”  
  
“Yes, and if you ever give Barton shellfish, the man’s entire face blows up like a balloon by the way." He chuckled at the recollection. “The point is, you have to speak up if there’s something you need, understand?”  
  
“But you do so much for me already, I didn’t want to complain.” Peter gave a weak grin. “Plus, I had to know if Stark Raving Hazelnut was as bad as everyone said.”  
  
“And was it?”  
  
"No." Peter hugged his aching belly and moaned, “It was _my_ _favorite_.”  
  
A very exasperated Tony covered his face with his hands. “Kid, you’re gonna be the death of me."

**Author's Note:**

> (Credit to irondadtexts on tumblr for Peter’s ice cream flavor name and for loosely inspiring this story)


End file.
